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J W Lightbown

Publications and source records attributed to J W Lightbown.

34 records · Page 2Linked to original sources
PubMed1973

The international reference preparation of colistin methane sulfonate.

The international unit of colistin methane sulfonate has been defined by collaborative assay as the activity contained in 0.00007874 mg of the international reference preparation. The definition was based on results from 7 laboratories in 5 countries which carried out assays against their existing national standards. Because of the complex heterogeneity in composition of this antibiotic the international reference preparation was not designated as an international standard.

Colistin↗
PubMed1973

The second international reference preparation of lymecycline.

The second International Reference Preparation of Lymecycline was established. Nine laboratories in 8 countries collaborated in assaying its potency in terms of the first International Reference Preparation, of which stocks had become exhausted. The best estimate of potency was taken to be 948 IU/mg, which was the unweighted geometric mean of a total of 124 assays. On this basis, the International Unit of lymecycline was defined as the activity contained in 0.0010548 mg of the second International Reference Preparation.

International Cooperation↗
PubMed1973

The second international reference preparation of procaine benzylpenicillin in oil with aluminium monostearate.

The second International Reference Preparation of Procaine Benzylpenicillin in Oil with Aluminium Monostearate was established in replacement of the first international reference preparation. The blood-level duration test (WHO Requirements for Biological Substances, No. 9), used to evaluate batches of manufactured material in relation to this reference preparation, was revised to relate to the new reference preparation. Thus a batch now passes the test if the lower confidence limit of the ratio is greater than 0.45, instead of 0.50-the value that related to the first international reference preparation. This change will ensure that material passing the test in the future will be of the same quality as in the past.

Aluminum↗
PubMed1973

The second international standard for tetracycline.

A second international standard has been established to replace the first International Standard for Tetracycline, stocks of which were depleted. The International Unit of tetracycline is defined as the activity contained in 0.00101833 mg of the second International Standard, corresponding to a potency of 982 IU/mg. These values were assigned on the basis of the results of an international collaborative assay carried out by laboratories in 19 countries. Most of the assays were by diffusion techniques; a few were by turbidimetric methods. Both procedures gave statistically valid assays but there was some heterogeneity of repeated estimations within a laboratory and also some heterogeneity of the mean estimates from each laboratory. The agreed defined potency was the unweighted mean of 281 individual assays; the confidence limits were 978-986 IU/mg.

International Cooperation↗
PubMed1973

The international standard for rolitetracycline.

An International Standard for Rolitetracycline has been established and the international unit of this antibiotic defined as the activity contained in 0.001004 mg of the international standard. The definition of the international unit was based on the results of a collaborative assay in which 8 laboratories in 6 different countries participated; a total of 133 assays were performed. The assay was in terms of the Working Standard of the USA Food and Drug Administration; mean potencies for individual laboratories varied within a range of only 2% of the mean for all assays although 7 different test organisms were used in both diffusion and turbidimetric assays. Individual assays, however, provided potencies that varied within a range of 40%.

International Cooperation↗
PubMed1972

International standards and international reference preparations: amphotericin B, vancomycin, capreomycin, cefalotin, demethylchlortetracycline, gentamycin, gramicidin S, kanamycin and kanamycin B, lincomycin, lymecycline, methacycline, paromomycin, rifamycin SV, ristocetin and ristocetin B, spiramycin, and triacetyloleandomycin.

Each of the preparations described here was obtained and evaluated at the request of a WHO Expert Committee on Biological Standardization. Unless otherwise stated, a standard procedure was used to distribute the material into individual ampoules. The procedure was as follows. Upon receipt by the National Institute for Medical Research (NIMR), London, materials were stored temporarily in the dark at a temperature of -10 degrees C or lower, and protected from moisture. At a convenient time they were brought back to room temperature, mixed, and distributed into individual neutral glass ampoules so that each ampoule contained 50-100 mg of powder. If it was known that the material was light-sensitive non-actinic glass ampoules were used. After exhaustive drying in vacuum over phosphorus(V) oxide, the ampoules were either constricted (up to 1963) or fitted with capillary leak plugs, dried for a further period under the same conditions, filled with dry nitrogen, and sealed by fusion of the glass. The total drying period varied from 8 to 38 days according to the nature of the material. After they had been tested for leaks, the ampoules were stored in the dark at -20 degrees C.

Amphotericin B↗
PubMed1972

The second international standard for chlortetracycline.

As supplies of the International Standard for Chlortetracycline were practically exhausted, it was replaced. The potency of the second international standard was defined on the basis of an international collaborative assay comprising 157 individual assays performed in 9 laboratories in 6 countries. The mean potencies obtained in the participating laboratories, although they varied by only 7%, were heterogeneous. However, the mean potency for all the laboratories combined did not differ significantly from that of the first international standard. The International Unit for chlortetracycline was therefore defined as the activity contained in 0.001 mg of the second international standard, corresponding to a potency of 1 000 IU/mg.

Australia↗
PubMed1967

The international reference preparation of gramicidin.

The National Institute for Medical Research, London, was requested by the WHO Expert Committee on Biological Standardization to establish an International Reference Preparation of Gramicidin. This preparation was needed to standardize preparations of gramicidin containing predominantly gramicidin A, B and C, for which purpose the International Reference Preparation of Gramicidin S cannot be used. A batch of 100 g of crystalline gramicidin obtained in 1963 was distributed into ampoules in 55 mg amounts and dried in vacuo; the ampoules were then filled with dried nitrogen and sealed. The proposed international reference preparation was assayed biologically against the Master Standard of Gramicidin of the US Food and Drug Administration in 7 laboratories in 6 countries by turbidimetric methods.Significant curvature of the dose-response lines was found for most assays; no single transformation improved the linearity of assays from all laboratories. Although significant heterogeneity of potencies was obtained in 5 laboratories the mean potency ratios for all laboratories only varied over a range of 5% to 6%. The composition of the material is 7% gramicidin B, 50% gramicidin A and 25% gramicidin C; preparations of gramicidin containing appreciably higher concentrations of gramicidin B can be expected to give invalid assays against the international reference preparation.The material has been established as the International Reference Preparation of Gramicidin with a defined potency of 1000 IU/mg. The International Unit of Gramicidin is defined as the activity of 0.001 mg of the International Reference Preparation of Gramicidin.

Tyrothricin↗
PubMed1967

The second International Standard for Oxytetracycline.

The National Institute for Medical Research, London, was requested by the WHO Expert Committee on Biological Standardization to establish a second International Standard for Oxytetracycline, since stocks of the first International Standard were depleted. A batch of 500 g of oxytetracycline dihydrate obtained in 1963 was distributed into ampoules in 125-mg amounts; the ampoules were filled with dried nitrogen and sealed. The usual procedure of exhaustively drying the material was omitted since removal of water of hydration adversely affects stability of oxytetracycline dihydrate. The proposed replacement material has been assayed biologically in terms of the first International Standard in 9 laboratories in 7 countries by means of plate-diffusion and turbidimetric assays.Significant heterogeneity of the potencies obtained by the different laboratories and within 3 laboratories was not attributable to any known differences in assay technique; the weighted mean potencies obtained by all laboratories were within a range of +/-2% of the over-all mean potency.The potency of the second International Standard is approximately 3% less than that of the first International Standard but no significant difference in composition or purity could be detected by a variety of chemical and physical analytical methods. The material has been established as the second International Standard for Oxytetracycline with a defined potency of 880 IU/mg. The International Unit of Oxytetracycline is defined as the activity of 0.0011364 mg of the second International Standard of Oxytetracycline.

Oxytetracycline↗
PubMed1966

The second International Standard for Dihydrostreptomycin.

The National Institute for Medical Research, London, was requested by the WHO Expert Committee on Biological Standardization to establish a second International Standard for Dihydrostreptomycin, since stocks of the first International Standard were depleted. A batch of 500 g of dihydrostreptomycin sulfate obtained in 1961 was distributed into ampoules in 200-mg amounts and dried in vacuo; the ampoules were then filled with dried nitrogen and sealed. The proposed replacement material has been assayed biologically in terms of the first International Standard in seven laboratories in six countries by means of both plate-diffusion and turbidimetric assays.Significant heterogeneity of the potencies obtained by the different laboratories was revealed by statistical analysis; this heterogeneity might be caused by slight differences in the content of streptomycin of the two samples. The material has been established as the Second International Standard for Dihydrostreptomycin with a defined potency of 820 IU/mg. The International Unit of Dihydrostreptomycin is defined as the activity of 0.001219 mg of the Second International Standard for Dihydrostreptomycin.

Dihydrostreptomycin Sulfate↗
PubMed1966

The international standard for novobiocin.

The National Institute for Medical Research, London, was requested by the WHO Expert Committee on Biological Standardization to arrange a collaborative assay of the International Reference Preparation of Novobiocin in order to define the International Unit of Novobiocin. The collaborative assay showed that the International Reference Preparation was not suitable for use as an international standard, and a second preparation of 400 g of novobiocin acid was obtained in 1962. This second preparation was distributed into ampoules in 100-mg amounts and dried in vacuum. The ampoules were then filled with dry nitrogen and sealed. This material-the proposed international standard for novobiocin-has been assayed biologically in eight laboratories in six countries by means of plate diffusion assays; it has been assayed against the working standard preparation of the US Food and Drug Administration.The variation in the potencies obtained for the second proposed international standard for novobiocin were small and not significant. The material has been established as the International Standard for Novobiocin with a defined potency of 970 International Units per mg, and the International Unit has been defined as the activity contained in 0.001031 mg of the International Standard.

Bacteria↗
PubMed1965

The international standard for oleandomycin.

At the request of the WHO Expert Committee on Biological Standardization a batch of oleandomycin was submitted to an international collaborative study in six laboratories situated in four countries. In this study the material was assayed by plate diffusion methods, which varied in details of technique and design, against the US Food and Drug Administration's reference preparation for oleandomycin. On the basis of the results obtained the material has been established as the International Standard for Oleandomycin and the International Unit of Oleandomycin is defined as the activity in 0.001176 mg of the International Standard. The US Food and Drug Administration's standard and the International Standard are each part of the same parent batch of oleandomycin and the validity of such an assay has been compared with the more usual assay situation when there is some degree of difference between the preparations under comparison.

Biological Assay↗